Objective: Develop a Scanning ocular Aberration Measurement (SAM) system that solves five problems of current wavefront sensors. Current systems do not: 1) measure aberrations during accommodation; 2) allow variable density sampling depending on the severity of the ocular aberration; 3) monitor pupil size and location as a function of ambient illumination and accommodation. Further, 4) they limit the fitting of wavefront aberration to a Zernike expansion without evaluating the impact of the induced smoothing error or providing an alternative wavefront representation. Finally, 5) high cost limits market penetration. Specific Aims: Demonstrate feasibility by developing an optical breadboard and prototype software, integrating the software with the breadboard, and evaluating combined system performance. Methods: Bread-boarding and testing a see-through SAM system employing a movable micro-lenslet array coupled with a micro-aperture array, pupil monitoring system and improved analysis software. Health Relatedness: A cost effective instrument with improved utility capable of handling a broader range of patients quickens the transfer of proven laboratory technology to clinical care. Technological innovation: Variable spatial sampling dependent on need by scanning a micro-lenslet array coupled with a micro-aperture array, see-through design, pupil location monitoring as function of ambient illumination and accommodation, improved software utilities, lower cost.